Positioning apparatus



APrll 6, 1954 A. MASON ET AL PosIvTloNING APPARATUS 2 Sheets-Sheet lFiled March 28, 1952 Mam April 6, 1954 A. MASON ET AL POSITIONINGAPPARATUS 2 Sheets-Sheet 2 Filed March 28, 1952 08642 M/.Qadd

go 6040 Z0 0 40 60 80 /SRL A CEA/15N 7 OFA RMA TURF /Z FROM A/E/TRA LPOS/ 770W #WW/5 INVENTORS: ABRAHAM M. FUCHS BY AVREL MASON M R- mATTORNEY Patented Apr. 6, 1954 POSITIONING APPARATUS A vrelMasom-Brniingham, Mich., and Abraham l M. Fuchs, New York, N. Y.,assignors to Bendix Aviation Corporation, Detroit, Mich., a corporationof Delaware Application March 28, 1952, kSerial No. 279,132

1,1 Claims. l

This invention relates to a system-for controlling the operation of aplurality of output meinbers in accordance with the movements of asingle input member. More particularly, the invention relates to asystem for vsimultaneously and accurately guiding the movements of aplurality of tool heads in a complex pattern at high speeds inaccordance with the movements of a master cam.

During the past few years, rapid advances have been made in certainelds, such as in automatic transmissions and jet engines.v Theseadvances have caused the demands for products in the new elds to riseconsiderably. However,r industry has been experiencing diculty inmeeting euch demands because of the .GeneralesV machining problemsinvolved. Fer example, accuracies of one thousendth of an inch .er leesare beine, Specied for components .in producties instead of eecuraces ofseveral tliousandths of an inch as in previous prodllCS- Fllihmo'e? uhparis halle to be produced at relatively high speeds and in Somewhatcomplex Shapes.-

In eri-pending application Serial .N0f 272.591.. liled by Abraham M.Fuchs, dated February 2i), 1952, c system is diseIosed Vfor accuratelyguiding the cutter head of a tool over a workpiece in a complex patternin accordance with the move,- rnents of a master cam, The systemdisclosed in the above application accurately `Aguides the tool head bygenerating an electrical signal having an amplitude determined bythemovernents of the master cam. Although the amplitude of theelectrical signal is small, it controls the application of a largeamount of hydraulic power which drives the tool head. The tool-head inturn acts cn the electrical generator to minimize the amplitude of thegenerated signal. l t

This invention provides a systemV for simultaneously guiding thelmovements of a plurality d of tool heads in accordance with themovements of a master cam. The system operates on the tool heads byutilizing one control system similar to that disclosed above as a mastercontrol and by utilizing a plurality of similar systems as subsidiarycontrols for guiding the v different tool heads. Each subsidiary systemoperates in accordance with the instructions `from the master controlbut independently of the operation of the other subsidiarygsystems, Theaccuracy pror duced by simultaneously guiding a plurality of tool headsis almost as great ,as that produced in directing the movements of asingletool head.

An object of this invention is-to provide a system lfor:accurately-guidingazthe lmaniements of i a plurality of output membersin accordance With the movement of a single input member.

Another object of this invention is to provide a system of the abovecharacter for accurately directing a plurality of tool heads over thesurfaces of a plurality of workpieces in accordance with the patternprovided by a master cam.

A further object is to provide a system of the above character forsimultaneously cutting a plurality of Workpieces in a complex patternwith tolerances of as little as one thousandth ci an inch or less.

Still another object is to provide a system of the above characterrequiring only a single cam made from relatively soft and inexpensivematerial to accurately control the simultaneous production o1 similarpatterns in a plurality of Workpieces.

A still further object is to provide a system of the above characterrequiring the production of only a relatively small amount of power tocontrol the simultaneous applications of large amounts of power from aplurality of sources to accurately drive a plurality of tool heads in acomplex pattern.

Other objects and advantages will be apparent from a detaileddescription of the invention and from the appended drawings and claims.

In the drawings:

Figure l is a somewhat schematic diagram, partly in block form andpartly in section, illustrating the electrical, mechanical and hydraulicfeatures which together constitute one embodiment of the invention;

Figures 2 and 3 are enlarged sectional views of certain hydrauliccomponents shown in Figure l and illustrate in further detail theoperation of these components;

Figure 4 is a diagram of curves illustrating the linear reaction ofcertain electrical components shown in Figure l tothe movements of amaster cam; and

Figure 5 is a diagram oi curves illustrating the individual operation ofthe hydraulic components shown in Figures 2 and 3 and the advantagesaccruing vfrom obtaining a composite reaction of these components.

In one embodiment of the invention, a master cam l0 is adapted to movethe armature I2 of a transformer, generally indicated at I4, inaccordance with its own pattern. The armature |2- is Vmade from asuitable magnetic material and is disposed within a non-magnetic core itof the transformer It. A plurality o windings {8g-2.0, Hand `1M aredisposed on the core it such 3 'that the windings IB and 22 areinterleaved on one side of the core and the windings 2t and 24 areinterleaved in a similar manner on the other side of the core.

The inner terminals of the windings I8 and 20 are connected togetherandthe outer terminals of the windings are connected to the outputterminals of a signal generator 26. Connections are also made from theinner terminal of the winding 22 to the outer terminal of the winding 24and from the outer terminal of the winding 22 and the inner terminal ofthe Winding 24 to the input terminals of an amplifier 28.

Signals from the amplifier 28 are introduced to a detector 33, theoutput from which is applied either directly or through suitable D. C.ampliiers (not shown) to the outer terminals of windings 32 and 34 in atorque motor, generally indicated at 36. The inner terminals of thewindings'SZ and 34 are connected to an output terminal of a direct powersupply 38. The windings are dis posed on opposite legs of an armature 40pivotable at a central position on a pin 42, The armature is separatedby relatively small air gaps from yolres 44 and 46 forming part of ahorseshoe magnet (not fully shown).

Pistons 4S and 5|) are pivotably secured to the ends of the armature 4D.The piston 48 is housed within a sleeve 52 having an inlet conduit 54and an outlet conduit 56. A connectingconduit 58 is provided in thesleeve 52 above the inlet lconduit 54, and a connecting conduit Sil isprovided in the sleeve intermediate the conduits 54 and 55. spools c4,6E and 68 are provided on the piston 48 so as to be adjacent theconduits 53, 65 and 56, respectively, in the inoperative position of thepiston.

A portion lt connects the spools tt and t8. lhe portion 'IIJ has arelatively steep indentation 'I2 (l'ligure 2) adjacent the spool 66 anda relatively shallow indentation 'I4 adjacent the spool 63. Theindentations I2 and I4 communicate with each other by a curved portionintermediate the indentations. An oblique cut 'I6 is made in the sleeve52 adjacent the indentation 12, and a rectangular cut iii is made in thesleeve adjacent the indentation `I4.

In a similar manner the piston 59 lits in a sleeve its having an inletconduit d2, an outlet conduit 35i and connecting conduits SG and 88similar to the conduits T24, 56, 58 and respectively. Spools et, t2 and94 similar in construction and disposition to the spools E4, S6 and Se,respectively, are provided on the piston 5t. A portion 96 correspondingto the portion 'It connects the spools 52 and $4.

A channel 98 communicates with both the conduits di! and 88 and achannel Hin communicates with the conduits 5E and 88. The channels 9!and Ill@ lead to opposite faces oi' a piston |22 in a ram, generallyindicated at |04. The piston |02 drives a rod |06 connected to the coreI6 of the transformer I4 and to the perimeter of a wheel |08.

A plurality of bell crank levers III] are connected at spaced intervalsto the periphery of the wheel IIIll. Each lever IIU is pivotable at anintermediate position on a fixed bracket H2. At its outer end, eachlever I Iil is pvotably secured to an armature ||4 of a transformer,generally indicated at I I6. Each transformer I II has a core ||8similar to the core IB of the transformer I4 and also has a plurality ofwindings wound on the core I8 in a manner similar to the windings I8,20, 22 and 24 of the transformer I4.

The output from each transformer I IB is introacvaoc duced, throughamplifiers and detectors similar to the amplier 28 and detector Sii, toan associated torque motor, generally indicated at |20. Each torquemotor |26 is similar in construction to the torque motor 36 and isadapted to operate on force-compensated valves similar to the valvesdisclosed above. Pistons |22 in rams, generally indicated at |24, aredriven in accordance with the operation of the force-compensated valves.rllhe pistons E22 and the rams |24 are similar to the piston |02 and ram|l4, respectively.

Each piston |22 is connected to a rod |26 adapted to drive the head |28of a tool (not shown). A cutter |30 is provided on each of the toolheads |28 to cut a workpiece |32 adjacent the cutter in accordance withthe movements of the head. Each head |28 is also Iconnected to the coreof the transformer I i d associated with it, so as to drive the core inaccordance with the movements of its associated piston |22.

In its neutral position, the armature I2 is positioned intermediate thesecondary windings 22 and 24 of the transformer I4. Because Ot thisintermediate positioning and because of the symmetrical arrangement ofthe windings 22 and 24, voltages of equal magnitude and oppositepolarity are induced in the windings by the current flowing through theprimary windings it and 2t from the signal generator 26. Since thevoltages have an equal magnitude and opposite polarity, they arecancelled when introduced to the amp-liner 23.

When the armature I2 is moved to either side of its neutral position bythe cam IQ, the voltages induced in the secondary windings 22 and 24 nolonger have equal amplitudes. The difference between the inducedvoltages is substantially proportional to the displacement of thearmature I2 from its neutral position because of the symmetricaldisposition of the windings 22 and 24 on the non-magnetic core Iii.

In one particular embodiment of the transformer I4, a linearrelationship exists between the signal from the transformer and thedisplacement of the armature I2 with errors of less than 1% for armaturedisplacements up to 40 mils from each side of the neutral position. Asubstantially linear relationship exists in this embodiment with errorsslightly greater than l for armature displacements as high as il() mils.The linear relationship for this embodiment between the output signalsfrom the ansformer and the armature displacement is illustrated at |35and |38 in Figure 4 for cach side from the neutral position. In otherembodiments of the transformer I4, the difference between the voltagesinduced in the windings 22 and 2s may be substantially proportional todisplacements of the armature I2 for armature movements considerablygreater than 8G mils. However, the error in such embodiments of thetransformer may he slightly greater than the error or 1% disclosedabove.

The difference signal passing through the amplier 2B is detected andthen introduced to the windings l32 and 34 as direct currentsproportionate to the amplitude of the signal. The currents are producedin a push-pull arrangement in the detector 39 such that the currentthrough the winding 32 is equal in amplitude but opposite in polarity tothe current through the winding 34. Because of the opposite polarities,the current through one winding aids the direct current passing throughthe winding from the power supply 38, and the current through the otherwinding opposes .thezdirect nurrentfrom the power supply.,

morimos Ilieresultant imbalance inth'e 'currents 'through the windings32 and r34 causes magnetic iields of unequal' strengths tobefprodu'cedbythe-currents. The magnetic fieldsacton'the 4varmature 40 to produceapivotalmovement offthe armature on thepin 42 proportionaltothefdifferencebetween the magnetic elds. When thelunbalance inthewindings 32 and 34 is in fsuch a direction as to produce a`counterclockwise pivotal-movement ofrthe armature 40, the:` piston`llimoves upwardly. This` causes the spools 04 and 05 rt'omove awayfromthe connecting `conduits 58 and 60,`respectively,- so that they nolonger block theconduits Asj aresult, a continuous hydraulic circuit isestablished which includes theinlet conduit54, the connecting conduit58, the channel `|f`,-therarn |04,` the channel 98, the connectingconduit 00and the outlet conduit 50; As the hydraulic fluid ows throughthe ram |04, it produces a force on'the piston|02 in a direction to movethe'piston -to theV right. Similarly,-the -piston |02-.m0ves to the leftwhen the piston 50 is driven upwardly asa result of a pivotal' movementby the armature 40 in a clockwise direction.

As will be seen inlFigure 3, a `slight gap |40 is produced between thespool 64 and the connecting conduit 50 as the Apiston 48 movesupwardlyinV Figure 1. Sincethegap |40 is relatively small,

theiluid passing from-the inlet conduit 54 to the conduit 58 convergesatthe gap. lThis causes the velocity of the fluid to increase at the gap|40, and the increase in `velocity of the iluid produces an increase influid.momentum. This increase in momentum in turn produces aforce-opposing any increase in the Width of the gap |40; Since the fluidflows through ythe gap |40 at-anoblique angle relative to the axis of4the piston 48 land sleeve 52, the opposing-force producedby ltheiluidhasa component along the piston axis. Y The axial components of -iorce arevillustrated at |42 and |44 in Figure for fluid pressures of 1,000and-2r,000lbs.

per square inch, respectively.

rlhe opposing force produced by theuid at the gap iseffectivelycounteracted by a force produced by the fluid as it flowsthrough theconnecting `portion 10. The counteracting force is producedbecause lthe'velocity of the -fluid increases as the `fluid flowsiromthef relatively steep Aindentation 12 to the relatively shallowindentation V'14. This force also has a component along the axis of thepiston 48'. The vaxial components of the counteracting force areillustrated at`l46 and |48 in Figure 6 ior fluidpressure of `l,000 and2,000

lbs. per square inch, respectively.

vappli'cationserial No. 4V222`,`5'91,"1ed April 24, Y1951,

by Shih-Ying Lee.

vWhenthe piston '|02 moves t'olt'he'left or right in Figure'Litdrivesthe'core "I6 and 'thefwindings on the core in thesarriefdirectionBx'ffollowing :the piston |02; the'core II moves ina direction to reducethe relative'dis-placementfbetween vit'a'nd the-armature I2 aselectrical signal thatanayhave-'been produced. in the transformer I4.'yIn thisway aclosed servomechanism loop is 'produced in whicha'membersuch as'the piston |02 is driven .in'accordance `with an errorsignal and in a1 direction to minimize the signal.

f The-p'iston-fI-02 also drivesthe wheel |00 to produce a rotarymovement of thewheel. As the wheel moves,y it causes each of the bellcrank leversl I0 to pivot on itsA associated bracket I I2. The pivotalmovements of thediirerent levers I I0 in turn cause the differentarmatures I I4 to be moved axially in a pattern following thelmovementsof the wheel |085 Since the armatures I I4 all have substantiallysimilar movements, they cause' voltages of -substantially 'equalamplitudes to4 be induced inthe'diierenttransformers H5. These signalsactl on the pistons |22 in the rams |24 in a manner similar to thatdisclosed above for the piston |02,fthereby producing correspondingmovements for lthediiierent pistons.

The tool 'heads I 20 follow 4the movements of the pistons |22 and inturn move the cutters |30 towards and away fromthe Workpieces |32 in apattern determined by kthe rotational movements of the wheel |08. Sincethe-wheel |63 accurately follows thernovements of the master cam I0, allof the workpieces |32 are cut ina pattern corresponding substantiallyto-that determined by the master cam. In addition to moving the cutters|30, the headsIZS move-the cores `IIi and the windings on the coresinra-direction tominirnize the error signals produced in-thetransformers IIS.

The system disclosedabove has` several important advantages. It producesan electrical signal havinganiamplitude rcorresponding to the movementsof` an sinputrnernber, lsuch as the master cam l0. Although theelectrical signal has a relatively'sinall-amplitude, it accuratelycontrols the application civ a relatively large force, such'as thatproduced bythe ram |04. The large force inf'turn controls the movementsof a plurality of outputv members, such as the tool heads Because of theproduction of a-relativelysrnall signal to control the application of alargedriving force, the cam I0 has very little-pressure applied to itand very little heat developed in it from friction. As a result, the camcan be operated at relatively `high speeds `without any danger ,that itwill lose'its shape, `even when it is made from relatively vsoftand'inexpensivematerials. The accuracy is maintained in the system evenat high speeds since `the system responds f quickly and reliablytomovements of the cam I 0.

In-'additionv to the-above advantages, the apparatus disclosed above iscapable of providing high accuraciesV in the movements of the tool heads|28 for displacements of the heads considerably greater than the linearranges of the transformer I4 andthe transformers H5. For example, thetool heads |28 can accurately follow the movements of the'cam I0 througha distance of several inches even though the transformers produce asignal linearly related tofdisplacements of their armatures for armaturemovements of approximately only Y mils to each side of their neutral'pl'.isitions. This results `from the fact that the 'core I6 and thecores I |8 follow the move `ments of their associated armatures tominimize at all times the amplitudes of the signa-lsproduced in thetransformers.

' As disclosedabove, a plurality of tool heads are voperated by'utilizing one Aprimary control i subsidiary systems similar inconstruction to the primary system. Since both the primary andsubsidiary systems have accuracies of a very high order, the tool headsaccurately follow the movements of the master cam I even though they arenot directly controlled by the cam. Furthermore, the movements of thetool heads are accurate since each subsidiary system operatesindependently of the other subsidiary systems and has its own feedbackloop to correct any errors that may be produced in the movements of itsassociated tool head.

It should be realized that other input members than the cam ||l andother output members than the tool heads |28 may be utilized. Othervalves than the force-compensated valves disclosed above may also beutilized, but a greater force may be required to drive these valvesbecause the internal forces opposing the operation of the valves may notbe as closely compensated as in the valves disclosed above. In addition,other linkages then the wheel |08 and the bell crank levers Iii may beused to transmit motion from the primary to the subsidiary systems. For

example, the rod |06 may be provided with a plications, the principlesinvolved are susceptible i" of numerous other applications which will beapparent to persons skilled in the art. The invention is, therefore, tobe limited only as indicated by the scope of the appended claims.

What is claimed is:

1. Positioning apparatus, including, input means, means adapted to bedriven in accordance with movements of the input means, a plurality ofmotion sensors each including first and second members movable relativeto each other, each of the iirst members being responsive to variationsin the movements of the driven means to effectuate the production by themotion sensor of an electrical signal having an amplitude substantiallyproportional to such variations, a plurality of motors each actuated inaccordance with the amplitude of a diierent electrical signal, meansdriven by each motor, and a plurality of output means each adapted tofollow the movement of a diierent motor-driven means and to drive thesecond member in its associated motion sensor in a direction to reducethe amplitude of the generated signal.

2. Positioning apparatus, including, input means, a plurality of motionsensors each including i'lrst and second members movable relative toeach other to produce an electrical signal having an amplitude dependentupon their relative movement, the first member in a predetermined one ofthe sensors being responsive to movements of the input means to producea corresponding displacement relative to the second member, a motoractuated in accordance with the amplitude of the electrical signal,means driven by the motor and adapted to drive the second member in thepredetermined sensor in a direction to minimize the electrical signal,control means adapted to be displaced in accordance with the movementsof the driven means, the rst means in each of the sensors other than thepredetermined sensor being responsive to variations in the movements ofthe control means to effectuate the production by its sensor of anelectrical signal having .an amplitude substantially proportional tosuchvariations, a plurality of motors each actuated in accordance withthe amplitude of the electrical signal from a different one of the lastmentioned sensors, a plurality of means each driven by a diierent motor,and a plurality of output means each adapted to follow the movements ofa different driven means and to drive the second member in theassociated motion sensor in a direction to reduce the amplitude of thesignal produced by the sensor.

3. Positioning apparatus, including, input means, control means, meansfor displacing the control means in accordance with movements of theinput means, a plurality of rst members adapted to be driven by thecontrol means from a neutral position, a plurality of output means, aplurality of second members each associated with a diierent rst vmemberand adapted to be driven by an associated output means from a neutralposition so as to minimize any displacement between it and itsassociated ilrst member, a plurality of motion sensors, each including apredetermined one of the first members and a predetermined one of thesecond members and adapted to produce a signal having an amplitudesubstantially proportional to the relative displacement between themembers, means for applying a force on each output means to produce adisplacement of the output means, and means for controlling the forceapplied on each output means in accordance with the amplitude of thesignal generated by the associated sensor to produce a displacement ofthe output means substantially proportionate to the displacement of theinput means.

4. Positioning apparatus, including, input means, control means, meansfor displacing the control means in accordance with movements of theinput means, a plurality of motion sensors each having first and secondmembers movable relative to each other to produce an error signal havingan amplitude related to their relative displacement, the first memberbeing associated with the control means to provide a relativedisplacement betweenit and the second member in accordance withmovements of the input means, means for producing a plurality of drivingforces, means for controlling the amplitude of each driving force inaccordance with the amplitude of the error signal in an associatedmember, and a plurality of output means each adapted to be displaced inaccordance with the amplitude of a diierent driving force and to producea displacement of the second member in an associated sensor in adirection to minimize the amplitude of the error signal produced in thesensor.

5. Positioning apparatus, including, input means, a plurality of motionsensors each including first and second members movable relative to eachother to produce an error signal having an amplitude proportional totheir relative displacement, a plurality of driving means eachassociated with a different sensor, means for controlling the forceproduced by each driving means in Iaccordance with the error signalproduced by the sensor, a plurality of rams each having a piston adaptedto be displaced in accordance with the force produced by a diierentdriving means, the first member in a predetermined one of the sensorsbeing adapted to be displaced in accordance with the movements of theinput means so as to provide a relative displacement between it and thesecond member in the sensor and the second member being-'adapted to bedisplaced in accordac'zaoca ance with.v movements. of i. the; associatedpiston and :in ay direction to-minimize-the error-signal producedqbythe. sensor, control means adapted tol be` driven in accordancewithcthemovements of the piston associated With-the predetermined sensor and Vtoproduce corresponding movements of theA rst members relative to thesecondmembers in .the other sensors, anda plurality-of output means eachadapted to be driveninaccordancev with the movements of a diierentpiston and .to drive the second member in. an rassociated sensor indirection to minimize the error signal in thelsensor.`

6. Positioning apparatus, including, input means, Va plurality of motionsensors, each motion sensor. including rst and` second membersy moveablerelative to each other toproduce an error signal having an amplitudeproportional to their relative displacement, plurality of means forproducing drivingy forces, means for varying each driving force inaccordance with the amplitude of the error signalv from ay differentmotion sensor, the rst member in a predetermined one of the sensorsbeing associated With the input means to produce a relative displacementbetween it and the second member in accordance with themotion of theinput means, a piston associated With the predetermined motion sensei'and adapted to be driven by the driving force controlledr by the sensor,the second member in the predetermined sensorbeing adapted to be drivenby the piston in a direction to minimize the error signal, control meansadapted to be driven in accordance With the movements of the piston andAto control the movements ci the rst members in the sensors other thanthe predetermined sensor, and a plurality-of output means yeach adaptedto be displaced in accordance with a dilerent driving force and toproduce a displacement of the second member in an associated sensor in adirection to minimize the signal produced in the sensor.

'7. Positioning apparatus, including, input means, a motion sensorincluding first and second members movable relative` to Veach other toproduce an error signal having an amplitude dependent upon theirrelative displacement,Y the rst member in the sensor being ,adaptedtofollow the movements of the input means to produce a relativedisplacement between itand the output means, a ram including a piston,means for converting the error signal into a proportionate displacementof the piston in the ram, the second member in the motion sensor beingoperative in accordancey with movements of the piston to be displaced ina direction to minimizethe relative displacement between` it 'and thefirst member in the sensor, control means driven by the output means, aVplurality of motion sensors, each motion sensor in the pluralityincluding rst and second members movable relative` to eachother toproduce an error signal having an amplitude dependent `upon theirrelativedisplacement, the rst member in each sensor inthe pluralitybeing adapted to follow the movements of the control means, a pluralityor" rams each associatedlwith a dilerent motion sensor. andeachincluding a piston, means for converting .the error signal in eachmotion sensor. into a proportionate displacement of the piston in theassociated ram, and a plurality of output means each adapted to bedriven by a different piston and to drive the sec* ond member in anassociated sensor in a direction to minimize the relative displacementbetween the rst and second members in the sensor.

8. Positioning apparatus, including, input .1Q means, a, rnctionisensorinclud-ing linstand sec.-4 ondmembers movable-y relative toeach` otherto produce. an? electrical signal having an amplitude proportional totheir; relative displacement,- the iirst` memberbeing;'movablewrelative` to. the second member iin accordancewiththermovements ofthe inputfmeansya piston, means for converting .theelectrical signal into va proportionate movement. of- .theipistom :thesecond member being adapted; to dbe displaced `in accordance withmovements. poi rthespistonand in a direction to minimizethe. amplitudeof the electrical signal, control meansiadapted to be displaced inaccord* ance with the: movementsk of the piston, a plurali-ty of lirstmembers each adapted to be'driven bythe controlmeans from'a neutralposition, a plurali-ty of output means each associated witha differentrst member, a plurality or second members each adapted-to be drivenby'an associated output means from a neutral position so Ias to minimizeany displacement between it andfits associated first member, a pluralityof motion sensors, each including'a predetermined one of the firstmembers and a predetermined oneof the second members and adapted toproduce an elecn trical signal having an amplitude substantiallyproportional to the relative displacement between the members,valve-controlled means for applying a force on eachsoutput means so asto produce a displacement of theloutput means, and means operative byeach electrical signal to controlthe position of an associatedvalve-controlled means soas `to vary the force applied onv the output ymeans.. and thereby to produce a displacement of each output meanssubstantially'proportionate to the displacement of the'inputmeans.

9. Positioning apparatus, including, input means, a motion sensorincluding rst and second members movable relative to each other in apredetermined direction from a null position to provide alternatingelectrical signals having ain--v plitudes.substantially',proportional tosuch relative movements, the first member being associated Withthe'input `means to follow the movements of theinput means, a detectorfor converting the alternating'electrical signals into proportionatedirect signals, a hydraulic valve having a pair of pistons, a torquemotor operative in accordance with the direct signals to produce aproportionate. displacement of one of the valve pistons relative, totheother piston, a ram, a piston in the ram adapted to be displaced inaccordancev .With thev displacement of the valve pistons and to drivethe secondmember in the motion sensor in a direction to minimize theamplitude of the alternating electrical signals, a rotary converteradapted to be driven bythe ram piston, a pluralityof driven membersassociated with the rotarymember to convert the 'angular'movements oftherotarymember intocorresponding linear movements, .a plurality ofmotion sensors each including .first and second members. movablerelative to each other in apredetermined. direction from a null positionto provide. alternating electrical signals having, amplitudessubstantially Droportional to such relative movements, each ofthe iirst4members,l in theplurality of motion, sensors being, associated. with4 adifferent driven meansy to follow the movement of the'driven means, adetector associated with each motion sensor for converting thealternating electrical signals generated in the motion sensor intoproportionate direct signals, a plurality of hydraulic valves eachhaving a pair of pistons and associated with a diierent detector, aplurality of torque motors each operative in accordance with theproportionate direct signals from an associated detector to produce aproportionate displacement of one of the valve pistons in an associatedvalve relative to the other piston in the valve, a plurality of ramseach associated with a diierent torque motor in the plurality, a pistonin each ram adapted to be displaced in accordance with the displacementof the associated valve pistons, and a plurality oi output means eachadapted to be driven by an associated ram piston and to drive the secondmember in an associated motion sensor .in a direction to minimize therelative displacement between the first and second members in thesensor.

l0. Positioning apparatus, including, input means, a motion sensorincluding first and second members movable relative to each other togenerate an alternating electrical signal having an amplitudesubstantially proportional to the relative displacement between themembers, the iirst member in the motion sensor being adapted to followthe movements of the input means to produce a relative displacementbetween it and the second member in the sensor, a detector forconverting the alternating signal into a proportionate direct signal., aforce-compensated valve, a torque motor for producing a flow of iiuidthrough the valve in accordance with the amplitude of the direct signal,driving means operative in accordance with the iiow of huid through thevalve to drive the second member in the motion sensor in a direction tominimize the amplitude of the generated signal, a rotary member coupledto the driving` means to become angularly displaced in accordance withthe movements of the driving means, a plurality of driven memberscoupled to the rotary member to be linearly driven through distances inaccordance with the angular movements of the rotary member, a pluralityor motion sensors each including first and second members movablerelative to each other to generate an alternating electrical signalhaving an amplitude substantially proportional to the relativedisplacement between the members, the first member in each motion sensorbeing adapted to follow the movements of an associated driven member toproduce a relative displacement between it and the second member in thesensor, a plurality ci detectors each associated with a different motionsensor to convert into a proportionate direct signal the alternatingsignal generated by the sensor, a plurality of force-compensated valveseach associated with a different detector, a plurality of torque motorseach associated with a different valve to produce a flow of fluidthrough the valve in accordance with the amplitude of the direct signalfrom an associated detector, a plurality of output means each coupled tothe second member in a diilerent motion sensor, and a plurality ofdriving means each operative in accordance with the flow of iluidthrough an associated valve to drive an associated output means and thesecond member in an associated motion sensor in a direction to minimizethe amplitude of the signal generated by the sensor.

l1.' Positioning apparatus, including, input means, a motion sensorincluding iirst and second members movable relative to each other togenerate an alternating electrical signal having an amplitudesubstantially proportional to the relative displacement between themembers, the rst member in the motion sensor being adapted to follow themovement of the input means to produce a relative displacement betweenit and the second member, a detector for converting the alternatingsignal into a proportional direct signal, a valve, an annular sleeve inthe valve, an annular piston having an oblique indentation in itsannular surface to provide a force compensating for the force exerted bythe piston in opposing a movement away from the sleeve,` a torque motoractuated by the direct signal to produce a movement of the piston awayfrom the sleeve so as to produce through the valve a flow of iluidproportionate to such piston displacement, driving means operative inaccordance with the flow of iiuid through the valve to drive the secondmember in the motion sensor in a direction to minimize the amplitude ofthe generated signal, a rotary member coupled to the driving means to beangularly displaced in accordance with the movements of the drivingmeans, a plurality of driven members coupled to the rotary member to belinearly driven by the rotary member through distances dependent uponthe angular movements of the rotary member, a plurality of motionsensors each including iirst and second members movable relative to eachother to generate an alternating electrical signal having an amplitudesubstantially proportional to the relative displacement between themembers, the first member in each motion sensor being adapted to followthe movement of an associated driven member to produce a relativedisplacement between it and the second member in the sensor, a pluralityof detectors each associated with a diiierent motion sensor' to convertthe alternating signal from the sensor into a proportionate directsignal, a plurality of valves each associated with a different detector,an annular sleeve in each valve, an annular piston in each valve havingan oblique indentation in its annular surface to provide a forcecompensating for the force exerted by the piston in opposing a movementaway from the sleeve, a plurality of torque motors each actuated by thedirect signal from an associated detector to produce a movement of thepiston away from the sleeve in an associated valve so as to producethrough the valve a flow of fluid proportionate to such piston movement,a plurality of output means each coupled to the second member in anassociated motion sensor,

and a plurality of driving means each operative in accordance with thefiow of fluid through an associated valve to drive an associated outputmeans and the second member in an associated motion sensor in adirection to minimize the amplitude of the generated signal.

References Cited in the ille of this patent UNITED STATES PATENTS NumberName Date 833,689 Kitsee Oct. 16, 1906 1,877,605 Shivers Sept, 13, 19322,437,603 Hornfeck Mar. 9, 1948

